[Illuminated One]

Every god gets flat +15 on top of what he'd have in CBM (with the exception of the great sage, he has a bonus of 15 already and 25 is max - I think of making him immune to drain).
I actually don't know how it effects nation or pretender balance, and haven't done anything else.

Drain scale is -5 per tick, yes.
I don't think the magic scale is underpowered at all.
It doesn't give as much rp in the later stages of the game but your total research output will be lower, too. So as you can't force having level 8 or 9 in every path rp will be more valuable (and at magic3 15rp * 2 researchers * 60 turns = 1800 rp). Also you will get the full effect at turn 1 which has a huge impact on early game.
Hmm, maybe I should make it scale with the turn number, too, drain + bad research is no fun early on.